Process for the improvement of foundation soil with regard to natural soil and artificial fillings



W. DEGEN March 22, 1960 PROCESS FOR THE IMPROVEMENT 0F FOUNDATION SOIL.WITH REGARD TO NATURAL SOIL AND ARTIFICIAL FILLINGS (BOTTOMINGS FiledJan. 2, 1953 FIG.I

Unite PRGCESS FOR THE EMPROVEMENT OF FQUNDA- TION SfllL WITH REGARD TNATURAL SUKL AND ARTEFICIAL FILLENGS (BOTTOMINGS) Wilhelm Degen,Frankfurt am Main, Germany Application January 2, 1953, Serial No.329,333

3 Claims. (Cl. 61-36) The invention refers to a process for improvingfoundation soil for construction purposes. I

One of the oldest and best-known methods of dealing with non-stablefoundation soil, e.g. clay, lime, mud or muck, is to excavate and removethis nonstable soil, and replace it with a good supporting foundation,such as sand or gravel, if necessary by making use of a good bindingmaterial or poured concrete.

There are, however, many cases where such methods prove impractical,especially when dealing with a founda tion pit that must be pumped freeof water from time to time and requires expensive supporting.

Another method consists of removing such soft layers of soil by blastingso that the top layers of boulders and gravel are caused to sink(moorland blasting). In blasting, the firm top soil is blasted upwardlyand caused to fall back with force upon the softer soil beneath, thusforcing it laterally out. Blasting carried out in this manner may costonly less than half of the total cost of complete excavation but noabsolute assurance can be given that the soft non-stable soil will beeffectively removed.

In simple cases, soft foundation soils can be improved by forcing instones and gravel. To prevent the soil escaping from the side of thearea being worked, it is necessary to fence it in with planking andpiles. The effect of this method is very limited and does not extend toany great depth.

Compared to these aforementioned methods, the process of the presentinvention improves the foundation soil without actually removing thenon-stable layer. A load of particulate stable fill material, such asstones, is deposited on the top-soil and is forcefully shaken downthrough the non-stable soil to the firm sub-soil beneath, thus forcingup the soft soil between the interstices of the stones until a firmcarrying foundation of stones packed close together is formed within thesoft layer.

By shaking such a filling of stones into the soft soil, the stones forma stable base together with the soft soil which fills out theinterstices between the stones. The process has practical importanceespecially for the technique of foundation construction, for example, toimprove natural soft soils where, on the one hand, it is too expensiveto remove this layer but Where, on the other hand, stone or gravel isavailable at an advantageous price. It is also suitable for makingnon-stable embankments stable.

By using this process it is possible to construct dikes, railway androad embankments from generally unsuitably non-stable soil which willthus be prevented from settling.

This formation of a stable stone base makes it possible to constructembankments at a much steeper gradient with very little danger ofsliding occurring. The lateral embankment surfaces may be blocked in toprevent the soil from being forced out at the sides.

In carrying out this process the stone rubble or gravel can either beadded in individual loads and shaken into the soil until the requireddepth has been reached or the 2,929,219 atented Mar. 22, 1960 entireestimated quantity of fill material can be calculated and placed on topof the soft soil in a single load.

The most suitable equipment for this process are shaking implementswhich more or less grip the particulate fill material, for exampleperforated plates, grid type shaking implements and similar implementswhich permit the soft liquified soil to be forced upwardly between thestone material and to reach the surface. By fencing in the workingsurface with planks and piles, any lateral escape of soil can beprevented during the process of filling in the stone material.

The accompanying drawing illustrates in Fig. 1, the processof improvingfoundation soil with natural soil layers, and in step method of thepresent invention, a load of stones or gravel 3 is placed upon the softsoil layer and is then forcefully shaken into the soft soil by means ofa vibrating implement 4 which has secured thereto a grid 5. Thevibrating grid forces the particulate'fill material downwardly into thesoft soil, displacing the soft soil upwardly and sidewardly through theinterstices of the fill material to form a stable stone or gravel base 6whose interstices are filled with soft soil. As shown at the extremeleft of Fig. 1, this procedure is continued until the stable foundationhas reached the desired depth and the soft layer 2 has been transformedinto a load supporting, compact foundation 6.

in Fig. 2, a stable sub-soil is shown to support an embankment 7 of softsoil which contains a loose sprinkling of stones or gravel whoseproportion is insufficient to make the embankment load supporting orstable. Similarly to the method described in connection with Fig. l,stones or gravel 8 is placed upon the embankment and forcefully shakenthereinto by vibrating implement 10. The grid of the shaker llilprevents the particulate fill material 3 from escaping laterally as itis forced down into the soft soil. The procedure is continued until theentire. embankment consists of a stable foundation, such as shown at iin Fig. 2.

What I claim is:

1. In the method of improving the stability of soft 7 the soft soilfoundation and forcefully shaking the fill material into the soft soildown. to the stable sub-soil to force the soft soil upwardly andsidewardly through the interstices of the fill material.

2. In the method of forming muck into a stable foundation by addingparticulate stable fill material thereto, the steps of placing thestable fill material upon the muck and forcefully shaking the fillmaterial into the muck down to the stable sub-soil to force the muckupwardly and sidewardly through the interstices of the fill material.

3. In the method of forming muck into a stable foundation by addingstone rubble upon the muck and forcefully shaking the stone rubble intothe muck down to the stable sub-soil to force the muck upwardly andsidewardly through the interstices of the stone rubble.

The Use of Explosives for Settling Highway Fills, published by ,Du Fontand Company, Wilmington, Delaware, in 1932 (pages 10-11).

